In recent years, disk recording/reproducing apparatuses for optically recording/reproducing data are generally used in a wide variety of areas. The disk recording/reproducing apparatuses irradiate a laser light onto a recording surface of an optical disk medium such as a CD or DVD to read recorded data for reproduction or to optically record data. Disk media through which data are read and written by the disk recording/reproducing apparatuses include a CD-R, CD-RW, DVD-R, DVD-RW and the like.
There may occur a state in which recording is inadequately continued such as, for example, a state in which a servo tracking failure is made on a disk medium, a state in which a failure of a PLL for creating a recording clock or a state in which data is not provided in time for recording due to a higher recording speed on the disk medium than encoding speed of recording data. If recording is continued for the case in which such a state occurs, data cannot be recorded in a proper position where the data is to be recorded, or adequate object data cannot be correctly recorded.
If there occurs a state in which continued recording is inadequate, it is desirable to suspend the recording and then to start recording again. In this case, when the disk recording/reproducing apparatus uses a rewritable disk such as a CD-RW or DVD-RW, for which data can be overwritten without restriction, the data can be recorded again from the beginning. However, if the disk medium is a write-once disk such as CD-R or DVD-R, which allows data to be written only once, no overwrite is permitted. Thus, if storage of data is conducted again from the beginning, the disk medium cannot be reproduced therefrom.
In recent years, a larger number of write-once disks which are cheaper than rewritable disks have been used. However, cheap a disk medium may be, if a recording inadequate state occurs, it is not proper to determine the failed recording disk as a non-reproducible disk. On the contrary, if the recording has been suspended, it is desired to additionally record data from the recording-suspended position, in order to enable the data to be reproduced normally, if it is possible.
In order to add data to a disk medium, it is necessary to check in which position of the disk medium data is written and to identify a recording-suspended position. As a method for identifying the recording-suspended position of a writing-suspended optical disk medium, there is a technology described in Patent Publication JP-2003-308654A. In this technology, a syndrome calculation is performed using a transverse correction-code PI-parity to obtain the recording-suspended position, by determining whether the result of calculation includes an error, i.e., other than “0”, or no error, i.e., “0”.